The present invention relates to an improved method for forming a mold. More particularly, the invention relates to a method for producing a mold which can be used to form an encapsulated window assembly including a glass sheet and a gasket of a polymeric material which is formed to encapsulate the peripheral edge of the sheet.
Early window assemblies for automobiles often included a number of different elements, including adhesive sealants, mechanical fasteners, and exterior trim pieces. Subsequent window assemblies were developed in attempts to further improve on the earlier window assemblies. An illustration of a more recent window assembly is provided in U.S. Pat. No. 4,072,340, which is incorporated herein by reference. The window assembly disclosed in this latter patent includes a glass sheet, a frame, fasteners for affixing the assembly to a vehicle, and a casing or gasket of a molded material extending between the frame and the edge of the glass sheet. The purpose of such a gasket is to hold the glass sheet and the frame together.
In connection with the manufacture of window gasket assemblies of the more recent design, a mold apparatus is used. The mold typically used includes two mold sections which define a chamber for receiving the sheet. Such molds also include a gasket forming cavity formed by the cooperation of the mold sections, the sheet (around the peripheral edge of which a gasket is to be formed), and one or more seals positioned within the mold sections. An illustration of such a mold apparatus is provided in U.S. Pat. No. 4,561,625, which is incorporated herein by reference. Another illustration of such a mold apparatus is provided in U.S. Pat. No. 4,688,752, which is incorporated herein by reference.
A smooth and polished finish on any exposed surface of the window gasket assembly to be formed, usually the exterior facing surface of the window gasket assembly to be installed in an automobile window opening, is desired for aesthetic reasons. The facing surface of the metallic mold section which defines an exposed or exterior surface of the window gasket assembly is thus usually finished or polished so as to provide a smooth and finished surface corresponding to the exterior facing surface of the window gasket assembly. Since the mold sections typically are made of metal, it is undesirable for the glass sheet to contact the mold sections, as such contact leads to excessive breakage and scratching. Thus, a chamber in which the glass sheet is to be positioned is often formed in the interior of such molds so that the sheet, around the periphery of which an encapsulating gasket is to be formed, is not in contact with the mold sections.
As noted, conventional mold sections are made of metal. Hence, forming such mold sections typically requires a substantial amount of machining and hand labor so that the mold sections fit tightly together, precisely define the dimensions of the cavity in which a gasket is to be formed, and do not touch the glass sheet on the peripheral edge of which a gasket is to be molded. Such machining and labor generally takes a substantial amount of time and thus is fairly expensive. Because a different mold (and therefore a different pair of mold sections) is needed to form a window gasket assembly of a different shape (such as is needed for different windows or for different types of vehicles), the amount of time and money needed to prepare a number of different mold sections can be quite substantial. Finally, the costs of the metal used in making the mold sections means that such mold sections are more expensive and any scrap resulting from making such mold sections is costly.